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Johannes H. Knoetze - One of the best experts on this subject based on the ideXlab platform.
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Phase equilibria of methyl esters in supercritical propane
The Journal of Supercritical Fluids, 2015Co-Authors: Cara E. Schwarz, Q.h. Paulse, Johannes H. KnoetzeAbstract:Abstract High Pressure phase equilibria measurements using a static synthetic view cell for methyl decanoate, methyl dodecanoate, methyl hexadecanoate, methyl octadecaonate and methyl docosanoate in supercritical propane were conducted between 376.6 and 412.4 K at methyl ester mass fractions between 0.0178 and 0.660. The data show a linear increase in phase Transition Pressure with an increase in temperature at constant composition and, within the experimental range, total solubility was achieved below 8.1 MPa for all systems. Comparing the various data sets, an increase in phase Transition Pressure with increasing hydrocarbon backbone is noted, indicating that propane is able to fractionate a mixture of methyl esters.
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High Pressure phase equilibria of ethyl esters in supercritical ethane and propane
The Journal of Supercritical Fluids, 2013Co-Authors: Cara E. Schwarz, C. Schlechter, Johannes H. KnoetzeAbstract:Abstract The high Pressure phase equilibria of ethyl esters (ethyl decanoate/caprate, ethyl dodecanoate/laurate, ethyl tetradecanoate/myristate and ethyl hexadecanoate/palmitate) in supercritical ethane and propane have been measured in the temperature ranges 311–358 K (TR = 1.02–1.17) and 376–409 K (TR = 1.02–1.11), respectively. The measurements were conducted in a high Pressure view cell for ethyl ester mass fractions between 0.015 and 0.65. The results show a generally linear relationship between the phase Transition temperature and Pressure. No temperature inversions or three phase regions were observed. An increase in hydrocarbon backbone length leads to an increase in phase Transition Pressure. For ethane as supercritical solvent, this increase is linear. For propane as supercritical solvent, the nature of the increase was not quantified as the magnitude of the increase would be significantly influenced by the experimental measurement error as the observed increase is not very large. Comparison of the phase behaviour of ethyl esters with methyl esters shows very little difference, yet the phase Transition Pressure of ethyl esters in supercritical ethane and propane is significantly lower than those of the corresponding acids. The phase Transition Pressure of ethyl esters in ethane and propane is also lower than those in carbon dioxide.
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Phase equilibrium measurements of long chain acids in supercritical carbon dioxide
The Journal of Supercritical Fluids, 2012Co-Authors: Cara E. Schwarz, Johannes H. KnoetzeAbstract:Abstract Data on the phase behaviour of long chain fatty acids (octanoic, decanoic, undecanoic, dodecanoic, tetradecanoic, hexadecanoic and octadecanoic) in supercritical carbon dioxide is presented at temperatures between 308 and 358 K and Pressures up to 27 MPa. No three-phase regions were observed and at constant composition, an increase in temperature leads to an increase in phase Transition Pressure. An increase in hydrocarbon backbone length also leads to an increase in phase Transition Pressure. Comparison of the measured data with literature data of n-alkanes, 1-alcohols, methyl esters and ethyl esters of the same hydrocarbon backbone length shows that carbon dioxide is able to easily distinguish between acids and n-alkanes, methyl esters or ethyl ester and, with selection of the correct conditions, carbon dioxide is also able to distinguish between acids and 1-alcohols. However, unlike for propane, the phase behaviour of an acid in carbon dioxide does not mimic that of an alkane with double the number of carbon atoms, most probably due to the effect of the quadrupole moment of carbon dioxide.
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High Pressure phase equilibrium measurements of long chain alcohols in supercritical ethane
Journal of Supercritical Fluids, 2010Co-Authors: Cara E. Schwarz, A.j. De Villiers, C.b. Mcclune, G.j.k. Bonthuys, Andries J. Burger, Johannes H. KnoetzeAbstract:High Pressure phase equilibrium measurements of long chain 1-alcohols (1-decanol through 1-docosanol) in supercritical ethane and their prediction are presented. The data were measured in a high Pressure view cell above the melting points of these alcohols, i.e. between 308 and 356 K, and with 1-alcohol mass fractions ranging from 0.0173 to 0.648. The results show a linear relationship between the phase Transition Pressure and the system temperature. The phase Transition Pressure increases with increasing molecular mass of 1-alcohol at constant temperature and composition. Furthermore, a linear relationship exists between the phase Transition Pressure and the number of carbon atoms of the 1-alcohol, making it easy to predict phase Transition by simple interpolation within the experimental boundaries. Additionally, the state-of-the-art sPC-SAFT EOS model, as now typically included in process simulators, is unable to predict the phase equilibria, although it tends to give better results than the classic Peng Robinson EOS.
Cara E. Schwarz - One of the best experts on this subject based on the ideXlab platform.
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High Pressure Phase Equilibria of the CO2/Saturated Ethyl Esters Homologous Series
Journal of Chemical & Engineering Data, 2018Co-Authors: Cara E. SchwarzAbstract:A systematic study on the phase behavior of saturated ethyl esters with supercritical CO2 is presented. High Pressure phase behavior measurements for the systems CO2/ethyl decanoate, CO2/ethyl dodecanoate, CO2/ethyl tetradecanoate, and CO2/ethyl hexadecanoate were conducted in a static synthetic view cell in the temperature range 308–358 K. Phase Transition Pressures were measured in the range 5.86–23.01 MPa for ethyl ester mass fractions in the range 0.0174–0.657 and complement existing literature data. Throughout the temperature and compositional range measured, which encompassed the liquid phase, mixture critical region, and vapor phase, an increase in temperature leads to an increase in phase Transition Pressure with no temperature inversions or three phase regions observed. Additionally, an increase in hydrocarbon backbone length leads to an ever-increasing phase-Transition Pressure, suggesting fractionation of ethyl esters according to molecular mass with supercritical CO2 is possible. Finally, the ...
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Phase equilibria of methyl esters in supercritical propane
The Journal of Supercritical Fluids, 2015Co-Authors: Cara E. Schwarz, Q.h. Paulse, Johannes H. KnoetzeAbstract:Abstract High Pressure phase equilibria measurements using a static synthetic view cell for methyl decanoate, methyl dodecanoate, methyl hexadecanoate, methyl octadecaonate and methyl docosanoate in supercritical propane were conducted between 376.6 and 412.4 K at methyl ester mass fractions between 0.0178 and 0.660. The data show a linear increase in phase Transition Pressure with an increase in temperature at constant composition and, within the experimental range, total solubility was achieved below 8.1 MPa for all systems. Comparing the various data sets, an increase in phase Transition Pressure with increasing hydrocarbon backbone is noted, indicating that propane is able to fractionate a mixture of methyl esters.
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High Pressure phase equilibria of ethyl esters in supercritical ethane and propane
The Journal of Supercritical Fluids, 2013Co-Authors: Cara E. Schwarz, C. Schlechter, Johannes H. KnoetzeAbstract:Abstract The high Pressure phase equilibria of ethyl esters (ethyl decanoate/caprate, ethyl dodecanoate/laurate, ethyl tetradecanoate/myristate and ethyl hexadecanoate/palmitate) in supercritical ethane and propane have been measured in the temperature ranges 311–358 K (TR = 1.02–1.17) and 376–409 K (TR = 1.02–1.11), respectively. The measurements were conducted in a high Pressure view cell for ethyl ester mass fractions between 0.015 and 0.65. The results show a generally linear relationship between the phase Transition temperature and Pressure. No temperature inversions or three phase regions were observed. An increase in hydrocarbon backbone length leads to an increase in phase Transition Pressure. For ethane as supercritical solvent, this increase is linear. For propane as supercritical solvent, the nature of the increase was not quantified as the magnitude of the increase would be significantly influenced by the experimental measurement error as the observed increase is not very large. Comparison of the phase behaviour of ethyl esters with methyl esters shows very little difference, yet the phase Transition Pressure of ethyl esters in supercritical ethane and propane is significantly lower than those of the corresponding acids. The phase Transition Pressure of ethyl esters in ethane and propane is also lower than those in carbon dioxide.
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Phase equilibrium measurements of long chain acids in supercritical carbon dioxide
The Journal of Supercritical Fluids, 2012Co-Authors: Cara E. Schwarz, Johannes H. KnoetzeAbstract:Abstract Data on the phase behaviour of long chain fatty acids (octanoic, decanoic, undecanoic, dodecanoic, tetradecanoic, hexadecanoic and octadecanoic) in supercritical carbon dioxide is presented at temperatures between 308 and 358 K and Pressures up to 27 MPa. No three-phase regions were observed and at constant composition, an increase in temperature leads to an increase in phase Transition Pressure. An increase in hydrocarbon backbone length also leads to an increase in phase Transition Pressure. Comparison of the measured data with literature data of n-alkanes, 1-alcohols, methyl esters and ethyl esters of the same hydrocarbon backbone length shows that carbon dioxide is able to easily distinguish between acids and n-alkanes, methyl esters or ethyl ester and, with selection of the correct conditions, carbon dioxide is also able to distinguish between acids and 1-alcohols. However, unlike for propane, the phase behaviour of an acid in carbon dioxide does not mimic that of an alkane with double the number of carbon atoms, most probably due to the effect of the quadrupole moment of carbon dioxide.
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High Pressure phase equilibrium measurements of long chain alcohols in supercritical ethane
Journal of Supercritical Fluids, 2010Co-Authors: Cara E. Schwarz, A.j. De Villiers, C.b. Mcclune, G.j.k. Bonthuys, Andries J. Burger, Johannes H. KnoetzeAbstract:High Pressure phase equilibrium measurements of long chain 1-alcohols (1-decanol through 1-docosanol) in supercritical ethane and their prediction are presented. The data were measured in a high Pressure view cell above the melting points of these alcohols, i.e. between 308 and 356 K, and with 1-alcohol mass fractions ranging from 0.0173 to 0.648. The results show a linear relationship between the phase Transition Pressure and the system temperature. The phase Transition Pressure increases with increasing molecular mass of 1-alcohol at constant temperature and composition. Furthermore, a linear relationship exists between the phase Transition Pressure and the number of carbon atoms of the 1-alcohol, making it easy to predict phase Transition by simple interpolation within the experimental boundaries. Additionally, the state-of-the-art sPC-SAFT EOS model, as now typically included in process simulators, is unable to predict the phase equilibria, although it tends to give better results than the classic Peng Robinson EOS.
Dieter Strauch - One of the best experts on this subject based on the ideXlab platform.
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SrS: Phase Transition Pressure, Phase Transition Temperature
Semiconductors, 2017Co-Authors: Dieter StrauchAbstract:SrS. Temperature dependence of the B1–B2 Transition Pressure from PP-PW-GGA calculations within the quasiharmonic approximation [11S]
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SrO: Phase Transition Pressure, Phase Stability, Phase Diagram
Semiconductors, 2017Co-Authors: Dieter StrauchAbstract:SrO. B1-B2 phase diagram from PP-PW-LDA calculations in the quasiharmonic approximation [12S]
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MgTe: Phase Transition Pressure, Phase Stability, Equation of State
Semiconductors, 2017Co-Authors: Dieter StrauchAbstract:MgTe (high-Pressure phases). Equation of state from EDXRD experiments (open squares [95L]) and from PP-PW-GGA calculations in the B8 structure (solid squares) and B31 structure (stars) [08L]
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BaTe: phase Transition Pressure
New Data and Updates for several IIa-VI Compounds (Structural Properties Thermal and Thermodynamic Properties and Lattice Properties), 2014Co-Authors: Dieter StrauchAbstract:SrSe. Temperature dependence of the B1-B2 Transition Pressure from PP-PW-GGA calculations within the quasiharmonic approximation [11S]
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BaO: phase Transition Pressure, phase stability
New Data and Updates for several IIa-VI Compounds (Structural Properties Thermal and Thermodynamic Properties and Lattice Properties), 2014Co-Authors: Dieter StrauchAbstract:SrTe. Temperature dependence of the B1–B2 Transition Pressure from PP-PW-GGA calculations within the quasiharmonic approximation [11S]
John P Perdew - One of the best experts on this subject based on the ideXlab platform.
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testing density functionals for structural phase Transitions of solids under Pressure si sio2 and zr
Physical Review B, 2013Co-Authors: Bing Xiao, Jianwei Sun, Adrienn Ruzsinszky, Jing Feng, Robin Haunschild, Gustavo E Scuseria, John P PerdewAbstract:We have investigated the structural phase Transitions of crystalline Si (insulator-metal), SiO${}_{2}$ (insulator-insulator), and Zr (metal-metal) under Pressure, as a test of several density functionals for the exchange-correlation energy. While meta-generalized gradient approximations (meta-GGAs) such as revTPSS (revised Tao-Perdew-Staroverov-Scuseria) are more sophisticated than GGAs such as PBE (Perdew-Burke-Ernzerhof), and are more accurate without empiricism for atomization energies of molecules, lattice constants of solids, and surface energies, we confirm that these meta-GGAs tend to give smaller and less realistic Transition Pressures than the PBE GGA does. But we also show that the recent functionals of the meta-GGA made simple family (MGGA_MS) behave differently, predicting larger and often more realistic Transition Pressures. We suggest that further refinement of the meta-GGA can lead to a functional that is more accurate for properties of molecules and solids at equilibrium or under compression. We also show that, contrary to recent suggestions but in line with older ones, an accurate fundamental gap in the noninteracting band structure is not necessary for an accurate prediction of the Transition Pressure. Unlike the semilocal GGAs and meta-GGAs, and unlike the local density approximation also tested here, the screened hybrid functional HSE06 (Heyd-Scuseria-Ernzerhof) is fully nonlocal and predicts more realistic fundamental gaps. HSE06 is better than the semilocal functionals for the Transition Pressures of Si and SiO${}_{2}$, but seriously overestimates the Transition Pressure in Zr. Besides the Transition Pressures, we report the Transition energies and volumes, binding energy curves, and structural parameters at zero and Transition Pressure. Finally, we discuss how the performance of a functional can reflect its plottable exchange enhancement factor, and why the structural phase Transitions are especially challenging for approximate density functionals.
Gustavo E Scuseria - One of the best experts on this subject based on the ideXlab platform.
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testing density functionals for structural phase Transitions of solids under Pressure si sio2 and zr
Physical Review B, 2013Co-Authors: Bing Xiao, Jianwei Sun, Adrienn Ruzsinszky, Jing Feng, Robin Haunschild, Gustavo E Scuseria, John P PerdewAbstract:We have investigated the structural phase Transitions of crystalline Si (insulator-metal), SiO${}_{2}$ (insulator-insulator), and Zr (metal-metal) under Pressure, as a test of several density functionals for the exchange-correlation energy. While meta-generalized gradient approximations (meta-GGAs) such as revTPSS (revised Tao-Perdew-Staroverov-Scuseria) are more sophisticated than GGAs such as PBE (Perdew-Burke-Ernzerhof), and are more accurate without empiricism for atomization energies of molecules, lattice constants of solids, and surface energies, we confirm that these meta-GGAs tend to give smaller and less realistic Transition Pressures than the PBE GGA does. But we also show that the recent functionals of the meta-GGA made simple family (MGGA_MS) behave differently, predicting larger and often more realistic Transition Pressures. We suggest that further refinement of the meta-GGA can lead to a functional that is more accurate for properties of molecules and solids at equilibrium or under compression. We also show that, contrary to recent suggestions but in line with older ones, an accurate fundamental gap in the noninteracting band structure is not necessary for an accurate prediction of the Transition Pressure. Unlike the semilocal GGAs and meta-GGAs, and unlike the local density approximation also tested here, the screened hybrid functional HSE06 (Heyd-Scuseria-Ernzerhof) is fully nonlocal and predicts more realistic fundamental gaps. HSE06 is better than the semilocal functionals for the Transition Pressures of Si and SiO${}_{2}$, but seriously overestimates the Transition Pressure in Zr. Besides the Transition Pressures, we report the Transition energies and volumes, binding energy curves, and structural parameters at zero and Transition Pressure. Finally, we discuss how the performance of a functional can reflect its plottable exchange enhancement factor, and why the structural phase Transitions are especially challenging for approximate density functionals.
